Comparison of a modification of the ellman method to measure carbamate inhibition of acetylcholinesterase in plasma, erythrocytes and brain tissues in sprague dawley rats using two analytical systems.

Inhibition of the enzyme acetylcholinesterase (AChE) using a carbamate compound was measured in 30 Crl: CD(R)BR Sprague Dawley rats. Erythrocyte, plasma, and brain tissues were analyzed using modifications of the Ellman technique(1) on two different clinical chemistry analyzers. Both EDTA and heparin anticoagulated whole blood were used for the erythrocyte and plasma tests. Results demonstrated similar inhibition of the enzyme in all three tissues between the control and dosed groups using the two technique modifications and instruments. Final inhibition of plasma and erythrocyte AChE for the control vs. treated groups (males and females combined) was 89.5% vs. 82% and 39% vs. 38% for the Technicon AutoAnalyzertrade mark vs. the Boehringer Mannheim Hitachitrade mark 704, respectively. Inhibition of the left and right brain segments for the control vs. treated groups (males and females combined) was 35% vs. 39% and 33.2% vs. 29% for the Technicon and the Hitachi, respectively. All inhibitions were significant at the 5% level using two tailed Dunnett's t-Test. Hemolysates prepared from EDTA whole blood packed cells gave more consistent results on the Hitachi 704.

Determination of iodine by atomic-absorption spectrometry using the platinum-loop technique.

The use of a platinum-loop atomizer and an electrodeless discharge lamp has been applied to the atomic-absorption determination of mercury at the 183.0-nm resonance line. Oxygen was flushed from the light-path with argon, giving adequate readiation transmission characteristics and a sensitivity of 9 ppm of iodine for 1% absorption. The method is prone to both cationic and anionic interferences, but the use of cation-exchange and solvent-extraction procedures overcomes some of the problems.

Some considerations on spectral line profiles of microwave-excited electrodeless discharge lamps.

The problems of line broadening in microwave-excited electrodeless discharge lamps for the more volatile elements, P, S, I, Se, Zn, Cd and Hg are discussed in relation to their use in atomic-absorption and fluorescence spectrometry. Both theoretical and practical implications are considered.

Application of photon-counting in atomic-absorption spectrophotometry.

An analysis is given of the statistics of photon-counting as a means of making measurements in atomic-absorption spectrometry. It is concluded that the simple application of Poisson counting statistics may give an over-optimistic estimate of the error, since other sources of error, such as flame flicker and variable nebulization rate, may be more significant.

A simple non-selective detector for gas phase chromotography, using the measurement of reflected microwave power.

A non-selective detector is described which can be used in conjunction with the microwave-excited emissive argon plasma detector. The mode of operation is based on the measurement of reflected power and its use is demonstrated with respect to a range of component vapours and permanent gases. The limit of detection for nearly all the species investigated is in the nanogram range and the detector responded to all compounds examined.

Some optical studies with the air-acetylene flame.

The application of Schlieren and shadow techniques for the study of flame processes is discussed in relation to analytically useful premixed flames. The information obtained, particularly with shadowgraphs, may be correlated with the measured signals and signal noise in atomic-absorption and flame-emission spectrometry.

Electronic modulation of microwave-excited electrodeless discharge lamps for use in atomic-fluorescence spectrometry.

Electronic modulation of electrodeless discharge lamps has been investigated with respect to frequency of operation and modulation waveform. The optimal frequency of operation was found to be ca. 20,000 Hz, using a square waveform, and modulation was best achieved by adding the modulation waveform to the reference of the stabilizing element in the microwave power supply. Optimal operating conditions have been established for d.c. and a.c. modes of operation for several sources.

Molecular emission characteristics of various fluorides in a low-temperature-hydrogen diffusion flame.

A capillary burner supporting a nitrogen/hydrogen diffusion flame has been evaluated as a possible means of detection for several volatile fluorides after their gas-chromatographic separation. The fluorides of As, B, C, Ge, I, Mo, P, Re, S, Sb, Se, Si, Te and W were formed by the reaction of the element with chlorine trifluoride, and the intense molecular emission given by each was recorded. An attempt was made to identify the emitting species.

A microwave-excited emissive detector for gas chromatography Further studies with sulphur compounds.

Improvements in the design and operation of the microwave excited detector for gas chromatography have led to an increase in the sensitivity and a lowering of detection limits for sulphur compounds.

Analytical applications of ternary complexes-VIII An improved reagent system for the spectrophotometric determination of aluminium.

Aluminium ions form a ternary complex with Catechol Violet (CV) and cetyltrimethylammonium bromide (CTAB) in which an Al(3)+:CV:CTAB ratio of 1:2:5 is observed. The sensitivity of the binary complex between aluminium and Catechol Violet (615nm) = 1.50 x 10(3) l. mole (-1). mm(-1) is enhanced on ternary complex formation to (670nm) = 5.30 x 10(3) l. mole(-1). mm(-1). The colour is formed instantaneously, stabilizes within 20 min, and may be used for the detection of aluminium in the range O.27-54 pm in the presence of EDTA which prevents the interference of most ions. A benzoate extraction procedure for aluminium is used to prevent interference from hundredfold amounts of Cr(VI), Fe(II), Fe(III), Hg(II), Sb(III), Ti(IV) and acetate, but Be, Cr(III), rare earths, V(V), Zr and tartrate must be absent, as must high concentrations of phosphate and fluoride ions.

the microwave-excited emissive detector in gas-phase chromatography-I Some studies with sulphur compounds.

An examination is made of the characteristics of a microwave-excited emissive detector and its potential use in the gas chromatography of sulphur compounds. The column was operated slightly above atmospheric pressure (ca. 105 kN m (2)) and the microwave detector at a convenient reduced pressure (e.g., 13-40 mbar). It is concluded that the most sensitive and specific wavelengths for analytical purposes are not necessarily the same for all the sulphur compounds examined, viz. carbon disulphide, thiophen, thioglycollic acid, dimethylsulphoxide and sulphur dioxide. The spectra obtained for each compound with argon or helium as carrier gas were characterized and only the atomic lines due to sulphur at 190.0 and 191.5 nm, the CS system with a bandhead around 257.6 nm and the C(2) bandhead at 516 nm were shown to be common to the organic compounds (except CS for thioglycollic acid). Carbon disulphide was the most easily fragmented and gave a limit of detection of 0.2 ng of sulphur at 257.6 nm even with the low luminosity monochromator used. Thioglycollic acid was the least easily fragmented compound.

Studies in atomic-fluorescence spectroscopy--VIII. Atomic fluorescence and atomic absorption of thallium and mercury with electrodeless discharge tubes as sources.

Atomic-fluorescence measurements, with microwave-excited electrodeless discharge tubes as sources of excitation, are described for thallium and mercury. The limits of detection by atomic fluorescence are 0.12 ppm for thallium and 0.08 ppm for mercury; the corresponding limits by atomic absorption (using the same instrument and source) are 6 and 10 times as great. The preparation, operation and spectral characteristics of thallium and mercury discharge tubes are described and comparisons are made with a thallium hollow cathode lamp and thallium and mercury spectral discharge lamps.

Analytical applications of ternary complexes-VI Spectrophotometric determination of trace amounts of palladium.

Extremely sensitive and specific colour reactions in both aqueous and organic solutions are described for the spectrophotometric determination of palladium(II) ions. The methods are based upon ternary complex formation with 1,10-phenanthroline or pyridine, and Rose Bengal Extra. Themolar absorptivities are 5 x 10(4) (aqueous) and 1.25 x 10(5) (organic) in the presence of a 1000-fold molar excess of EDTA as mass masking agent. Under these conditions there is negligible interference with the pyridine-Rose Bengal Extra system from the 22 cations (including silver, gold and platinum) and seven anions investigated. Both colour reactions take place within 15 min and the complexes are stable for long periods.

Analytical applications of ternary complexes-VII Elucidation of mode of formation of sensitized metal-chelate systems and determination of molybdenum and antimony.

The ternary complexes which are formed when surface-active agents are added to various metal-dyestuff chelate systems are shown to be dependent on the formation of micelles. Spectrophotometric measurements indicate that true ternary complexes are formed with well defined structures and that the changes in absorption spectra produced are not due to simple adsorption of the binary metal-dye complex onto micellar aggregates. Some suggestions are made to account for the nature of the observed changes. The analytical potentialities of this type of system are illustrated by the formation of such complexes between molybdenum or antimony, Catechol Violet and cetyltrimethylammonium bromide, yielding molar absorptivities of 4.6 x 10(4) and 3.0 x 10(4) respectively.

Inorganic polarography in organic solvents-IV: polarography of metal oxinate complexes in various solvents.

The polarography of 24 metal oxinate complexes extracted into chloroform, IBMK, and ethyl acetate has been investigated, a methanolic solution of lithium chloride being used as base electrolyte. Only 15 complexes gave rise to reduction waves, and interference-free determinations have been developed for indium and thallium(III) in chloroform, and for bismuth, molybdenum and uranium in IBMK. The use of ethyl acetate offered no special advantages, and was the least selective of the three solvents used.

Studies in atomic-fluorescence spectroscopy-VII Fluorescence and analytical characteristics of arsenic, with a microwave excited electrodeless discharge tube as source.

The construction of an electrodeless arsenic discharge tube and its use for atomic-fluorescence studies is described. Cool nitrogen-hydrogen and argon-hydrogen diffusion flames as well as normal premixed flames are considered as atom reservoirs and the atomic-fluorescence emission at 15 different wavelengths is evaluated. The diffusion flames give the largest emission signals at arsenic concentrations below 200 ppm, but show a premature curvature at higher concentrations because of the presence of an abnormally high density of arsenic atoms. Above 200 ppm of arsenic, the premixed air-acetylene flame is superior. The limit of detection at 1890 A is 0.2 ppm of arsenic in the nitrogen-hydrogen diffusion flame and 1.0 ppm in the airacetylene flame. A long path-length diffusion flame is also particularly useful in atomic-absorption measurements because it absorbs very little radiation in the far ultraviolet region and gives an abundance of arsenic atoms.

Analytical applications of ternary complexes-V Indirect spectrophotometric determination of cyanide.

An indirect spectrophotometric method is proposed for the determination of cyanide down to 0.2 ppm. It is based on the fact that cyanide prevents the formation of the strongly absorbing ternary complex between silver(I), 1,10-phenanthroline and Bromopyrogallol Red in nearly neutral aqueous solution. Among 17 cations examined, only mercury(II) could not be tolerated. Zinc, cadmium and cobalt interfered only when present in large amounts. A 1000-fold molar excess (over cyanide) of 14 anions can also be tolerated. Bromide, iodide and thiocyanate interference is overcome by addition of lead nitrate, ammonium sulphate and barium nitrate, followed by centrifugation.

Some applications of microwave-excited electrodeless discharge tubes in atomic spectroscopy.

The need for an intense spectral line source in atomic absorption and atomic fluoresence spectroscopic measurements is discussed. Microwave-excited electrodeless discharge tubes would seem to satisfy all the essential requirements of these techniques. Their present state of development in the authors' laboratory is described in relation to methods of preparation, excitation conditions, and spectral characteristics of lamps. The application of certain discharge tubes in both atomic absorption and atomic fluorescence is briefly assessed, and the limits of detection obtained using commercial equipment at various wavelengths and in several flame types is presented.

Studies in atomic-fluorescence spectroscopy-VI The fluorescence characteristics and analytical determination of bismuth with an iodine electrodeless discharge tube as source.

The atomic-fluorescence characteristics of bismuth atoms in cool nitrogen-hydrogen and argon-hydrogen diffusion flames burning in air are described. Excitation is obtained from the non-resonance iodine line at 2061.63 A emitted by a microwave-excited electrodeless discharge tube operating at 2450 Mc/s. Fluorescence of the bismuth resonance line at 2061.70 A is observed and also direct-line fluorescence at 2697 and 3025 A. In addition thirteen other much weaker lines were observed and two unidentified lines at 2880 and 2680 A. The emissions at 2628 and 2938 A appear to arise from "thermally assisted direct line fluorescence". The most intense line at 3025 A permits linear-dependence analytical atomic-fluorescence measurements to be made in the range 0.1-200 ppm with a detection limit of 0.05 ppm and with no problems of source scatter. No interference was observed from hundred-fold concentrations of fourteen ions. Matrix effects from aluminium and magnesium were overcome by raising the temperature of the cool diffusion flames. A bismuth microwave-excited electrodeless discharge tube was used as a source for atomic-absorption measurement in air-hydrogen and air-propane flames at 2231A with a detection limit of 1 ppm and a linear-dependence analytical range of 10-100 ppm. With the iodine microwave-excited electrodeless discharge tube the detection limit for atomic absorption was 10 ppm at 2062 A.

Studies in atomic-fluorescence spectroscopy-V The fluorescence characteristics and determination of antimony.

Atomic-fluorescence of antimony may be generated in an air-propane flame by nebulizing aqueous solutions of antimony salts whilst irradiating the flame by means of a microwave-excited electrode-less discharge tube operating at 30 W. The strongest fluorescence is exhibited by the (4)S(11 2 ) --> (4)P(1 3 ) 2311 A resonance line and weaker signals are observed at the 2068 and 2176 A resonance lines and at four intercombination lines, at 2598, 2671, 2770 and 2878 A. A process of thermally assisted direct-line fluorescence is postulated to account for the otherwise inexplicable intensity of the 2598 A line emission. Atomic-fluorescence spectroscopy at 2176 A permits the determination of antimony in the range 0.1-120 ppm with a detection limit of 0.05 ppm. With the same equipment and source, the range of measurement for atomic-absorption was 6-120 ppm and the detection limit was 1 ppm. No interferences were observed from 100-fold molar amounts of Cd, Co, Cu, Fe, Hg, K, Mg, Mn, Mo, Na, NH(4), Pb and Zn or from arsenate, chloride, nitrate, phosphate and sulphate.